U.S. patent application Ser. No. 674,475 entitled "An Electronic Circuit Interrupter with Attached Terminal Connector Board" describes a main circuit breaker connected within a switchboard enclosure containing a plurality of branch circuit breakers. The main and branch circuit breakers each include individual terminal blocks that are arranged within the switchboard enclosure. The main and branch circuit breakers communicate with a central programming unit over a power-line communication network to provide supplemental protection features.
The branch circuit breakers described within the aforementioned U.S. Patent Application are so-called "smart" circuit breakers wherein each circuit breaker contains its own microprocessor and software support programs. The terminal boards connected with the individual circuit breakers provide the means for connecting with the power-line communication link that connects the central programming unit with the main and branch circuit breakers.
With Zone-Selective-Interlock function, wherein an upstream circuit breaker is restrained from responding to interrupt a protective circuit until a downstream circuit breaker closer to the source of the fault has responded, there must be some means for communicating between the upstream and downstream circuit breakers.
U.S. Pat. No. 4,468,714 entitled "Zone Selective Interlock Module for Use with Static Trip Circuit Breakers" describes one such Zone-Selective-Interlock system using hard-wired connections between the upstream and downstream circuit breakers.
"Load Selection" as described herein concerns prioritizing the electrical equipment loads that are connected with distributed branch circuit breakers whereby selected circuit breakers are actuated to interrupt operating power to non-essential equipment while the operating power to those circuit breakers connected with essential equipment such as computers, emergency lighting and medical apparatus is maintained.
U.S. Pat. No. 4,672,501 entitled "Circuit Breaker and Protective Relay Unit" describes a "smart" circuit breaker which includes a microprocessor programmed to perform the Load Selection function.
U.S. Pat. No. 4,589,052 entitled "Digital I.sup.2 T Pickup, Time Bands and Timing Control Circuits for Static Trip Circuit Breakers" describes an electronic trip unit useful for overcurrent protection, which does not include a microprocessor. When such electronic trip units are used as branch circuit breakers it would be highly advantageous to provide such circuit breakers with Zone-Selective-Interlock and Load Selection Functions.
U.S. Pat. No. 4,991,042 entitled "Digital Circuit Interrupter with Keypad Data Entry and Display" describes a smart circuit breaker containing its own microprocessor and associated circuitry for entering trip parameters to the electronic trip unit and displaying the trip parameters along with voltage and ampere ratings, upon command.
Accordingly, one purpose of the invention is to use a smart circuit breaker as the main circuit breaker within a switchboard or panelboard enclosure along with a plurality of distributed branch circuit breakers containing electronic trip units such as described in the aforementioned U.S. Pat. No. 4,589,052.